Floral Longevity and Attraction of Arctic Lupine, Lupinus arcticus: Implications for Pollination Efficiency

Pollination by insects is a mutualistic relationship in which flowers receive pollen for reproduction while pollinators are rewarded with pollen or nectar. Floral longevity (the period an individual flower blooms) and floral attraction (the period during which pollinators are attracted to the flower, often indicated by petal colour) both play prominent roles in plant and pollinator success. This study investigated whether floral longevity and floral attraction were mediated by pollination type in arctic lupine (Lupinus arcticus S. Wats.), a common herbaceous perennial in northwestern North America. Flowers were either open to pollinators, cross-pollinated by hand, or bagged to prevent cross-pollination, and floral longevity, seed set, and flower colour were observed. Open and hand-pollinated flowers had significantly shorter floral longevities and higher percent fruit sets than bagged flowers. A colour change of the banner petal marking from white to pink occurred in some flowers and was a signal of floral attraction, as pollinators preferentially visited pre-change flowers. Pre-change flowers contained more pollen and were less likely to have been injured by herbivory than post-change flowers, yet the colour change was not related to pollination type or fruit set. Pollination-induced shortening of floral longevity is likely an adaptation to limited plant resources and pollinator visitation rates. For L. arcticus, this could be influenced by short growing seasons and low annual temperatures in the study area. In the face of climatic changes and shifting species phenologies, the mediation of floral longevity by pollinators could decrease temporal mismatch between plants and their pollinators, yet the many factors at play make this difficult to accurately predict.

Advertisements 1: Visual Signals and Floral Color

This chapter examines how color interacts with the other visual signals from floral size, shape, and outline in enhancing floral attraction to visitors. Visual attraction by flowers is linked to floral shape and size. For most pollinators, color and color patterns are attractive. Most of today’s key pollinating taxa have good color vision, and flowers should have been selected to interact with their visitors’ visual abilities. The chapter first considers floral pigments and floral color before discussing the problems of defining and measuring color in flowers. It then explains how animals perceive flower color and proceeds by analyzing color preferences in animals, along with the ecology and evolution of flower color and color preferences. It also explores nectar guides, how floral color change can control pollinators, and other visual cues used for advertisement. Finally, it asks why flower colors diverge, citing the role of selection.